Conventionally, a sputtering apparatus was used in the film-forming step in manufacturing, e.g., semiconductor devices. As a result of recent trends for micro-fine wiring patterns, the sputtering apparatus to be used for this kind of use is strongly required to be able to perform film forming at good coating characteristics relative to the micropores of high aspect ratio over the entire surfaces of the substrate to be processed, i.e., to improve the coverage.
Generally, in the above-mentioned sputtering apparatus, magnet assembly having provided therein a plurality of magnets are disposed, e.g., behind the target (the side lying opposite to the sputtering surface) by alternately changing the polarity. By means of this magnet assembly a tunnel-shaped magnetic field is caused to be generated in front of the target (on the side of the sputtering surface). Electrons ionized in front of the target and secondary electrons generated by the sputtering are collected. Plasma density is thus increased by increasing the electron density in front of the target.
In this kind of sputtering apparatus the target is preferentially sputtered in the region, out of the entire target, to be affected by the magnetic field. Therefore, if the above-mentioned region is present, e.g., in the neighborhood of the center of the target from the viewpoint of stability of discharging and the improvement in the utilization efficiency of the target, the amount of erosion of the target at the time of sputtering becomes large near the center thereof. In such a case, in the peripheral portion of the substrate, the particles of the target member sputtered from the target (e.g., metal particles, hereinafter referred to as “sputtered particles”) are incident at an inclined angle and get deposited thereon. As a result, in case the conventional sputtering apparatus is used for the above-mentioned film forming, there has conventionally been known that a problem arises of asymmetry in coverage especially in the peripheral portion of the substrate.
In order to solve this kind of problem, there is known in patent document 1 a sputtering apparatus in which: a first sputtering target is disposed above a stage on which is mounted a substrate inside a vacuum chamber substantially in parallel with the surface of the stage; and a second sputtering target is disposed at an angle to the surface of the stage slantingly above the stage, i.e., a sputtering apparatus which is provided with a plurality of cathode units.
However, if a plurality of cathode units are disposed inside the vacuum chamber as described in the above-mentioned patent document 1, there are disadvantages in that the arrangement of the apparatus becomes complicated and that the cost becomes high due to an increased number of parts because the sputtering power supply becomes necessary depending on the number of targets.    Patent Document 1: JP-A-2008-47661